An RFID tag that communicates information with an RFID reader/writer includes a receiving unit that receives ID information; a memory unit that stores the ID information; a table that stores a correspondence relation between a change in the ID information and a moving direction; a determining unit that refers to the table to determine a moving direction from ID information received by the receiving unit and previously received ID information stored in the memory unit; and a signal generating unit that sends an interruption signal to a control unit driven by electric power supplied from a battery when the moving direction is determined by the determining unit, and stops generating the interruption signal when the moving direction is not determined by the determining unit.